In a typical cellular network, also referred to as a wireless communication system, User equipment, UEs, communicate via a Radio Access Network, RAN, to one or more core networks, CNs.
A user equipment is a mobile terminal by which a subscriber may access services offered by an operator's core network and services outside operator's network to which the operator's RAN and CN provide access. The user equipment may be for example communication devices such as mobile telephones, cellular telephones, smart phones, tablet computers or laptops with wireless capability. The user equipment may be portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another mobile station or a server. User equipments are enabled to communicate wirelessly in the cellular network. The communication may be performed e.g. between two user equipments, between a user equipment and a regular telephone and/or between the user equipment and a server via the RAN and possibly one or more CNs, comprised within the cellular network.
The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g. a Radio Base Station (RBS), which in some RANs is also called eNodeB (eNB), NodeB, B node or network node. A cell area is a geographical area where radio coverage is provided by the radio base station at a base station site. Each cell area is identified by an identity within the local radio area, which is broadcast in the cell area. The base stations communicate over the air interface operating on radio frequencies with the user equipment within range of the base stations. It should be noted that a base station may serve one or more cells, also referred to as cell carriers, within its cell area.
According to one example, a RAN may be based on a Wideband Code Division Multiple Access/High Speed Packet Access, WCDMA/HSPA, technology. In such a RAN, there are different ways to send data in downlink transmissions to a user equipment when the user equipments is operating in an active state, e.g. a CELL_DCH state. Note that this active state is the opposite to an idle state, e.g. a CELL_FACH state. In the idle state, the user equipment only communicate using common channels, while in the active state, the user equipment may communicate using both common and dedicated channels.
In the active state, a Dedicated Physical CHannel, DPCH, also sometimes referred to as a DCH channel, or a High-Speed Downlink Shared CHannel, HS-DSCH, may be used in addition to the common channels. Using the HS-DSCH channel is usually referred to as HSDPA operation, and unlike the DPCH, the HS-DSCH channel is shared amongst multiple user equipments. The HS-DSCH channels may thus be referred to as a shared channel as oppose to a dedicated channel, such as, DPCH.
In practice, the DPCH and HS-DSCH channels may co-exist, i.e. be used simultaneously by the network node, for downlink transmissions. This means that at a given time instant, a network node may transmit both DPCH and HS-DSCH transmissions to user equipments within the same cell.
However, this also means that the available resources of the network node, such as, channelization codes, downlink transmission, DL TX, power, etc., needs to be shared between the DPCH and HS-DSCH transmissions. Also, since the resources of the network node that are allocated to the HS-DSCH transmissions are shared, they are therefore used as a common resource. This means that for each Transmission Time Interval, TTI, the common resource may be dynamically shared between the user equipments in the same cell. This enables a large part, e.g. some or all, of the common resources of the network node to be allocated to one or more specific user equipments in a given TTI. On the contrary, the resources of the network node that are allocated to the DPCH transmissions are used as a dedicated resource.
For the HS-DSCH downlink transmissions, the possibility to dynamically share and allocate the resources of the network node as a common resource in a cell is particularly beneficial for packet data. This is because packet data generally have bursty characteristics resulting in a highly varying resource need for the user equipments in the cell, and because dynamically deciding to which user equipment in the cell the resources of the network node is to be allocated allows for more resources to be given to those user equipments in the cell having data in their data priority queues at the network node that needs to be transmitted. This will thus increase the overall efficiency of the downlink data transmissions in the cell.
This also means that the more resources of the network node, i.e. channelization codes, DL TX power, etc., that are available for transmissions in the cell, the more payload data, i.e. information bits, may be sent on the HS-DSCH channel in the cell. While the number of channelization codes available for HS-PDSCH downlink transmissions are limited to 15 SF16 HS-PDSCH codes, the available DL TX power is only dependent of the capabilities of the power amplifier that is used for physically transmitting the data in the cell.
In a cell, the total DL TX power, i.e. the total cell power, needs to be shared between all physical channels. This comprises the physical channels associated with the DPCH channels, such as, e.g. F-DPCH, DPDCH and DPCCH. It also comprises the physical channels associated with the HS-DSCH channels, such as, e.g. HS-PDSCH, HS-SCCH. In order to maximize the HSDPA performance, i.e. the use of the physical channels associated with the HS-DSCH channels, while at the same time maintaining the quality of the dedicated channels, i.e. the quality of the physical channels associated with the DPCH channels, a common approach is to allow HS-DSCH transmissions in a cell to use the remaining DL TX power once DL TX power has been allocated for the common and dedicated channels in the cell.
One example of this common approach is illustrated in FIG. 1. Here, the common channels are allocated a constant amount of the total DL TX power, while the amount of the total DL TX power to the dedicated channels is power controlled. Thus, the remaining DL TX power available for the HS-DSCH channel will vary.
Given the amount of DL TX power in a cell and the number of channelization codes available for the HS-DSCH downlink transmission in a cell, the network node may determine, for each TTI, to which user equipment in the cell data shall be transmitted to on the downlink on the HS-DSCH channel, and how much data which should be transmitted in the TTI. The amount of data that may be sent, or the Transport Block Size, TBS, that is used, in a single TTI is commonly based on the available number of channelization codes in the cell and the DL TX power available to the HS-DSCH transmission in the cell.
For every TTI, or scheduling opportunity, the network node may determine how much DL TX power that may be used for the HS-DSCH transmission, i.e. PHS, in the TTI for a cell based on the following formula (Eq. 1):PHS=Ptotal cell power−Pdedicated channels−Pcommon channels  (Eq. 1)
Here, the Ptotal cell power is the total DL TX power that is allocated to the cell, the Pdedicated channels is the DL TX power that is allocated to the dedicated channels in the cell, and the Pcommon channels is the DL TX power that is allocated to the common channels in the cell. The common channels may comprise e.g. CPICH, E-AGCH, E-HICH, HS-SCCH, etc. Once the available PHS and the available number of channelization codes are known for the cell, it is straightforward for the network node to determine how much data that may be sent in the TTI for the cell based on a specific Quality of Service, QoS. The specific QoS may be measured in terms of e.g. a target BLock Error Rate, BLER.
However, this means that, for example, when there is not enough data in the user equipment's priority queues at the network node for the cell, e.g. when data may be transmitted with the desired QoS-level utilizing less power than PHS, the result may be that not all of the available PHS will be used for HS-DSCH downlink transmission in the cell for the TTI.
For these cases, it may be possible in a network node having one or more radio units comprising one or more power amplifiers to dynamically share the DL TX power that may be used for the HS-DSCH transmission, i.e. PHS, in a TTI amongst cells that are sharing a power amplifier in a radio unit of the network node. This dynamical sharing of HSDPA power may occur e.g. when one or more cells would benefit from additional HSDPA power, i.e. having enough data to transmit in their RBS buffers, at the same time as one or more of the other cells does not use all their HSDPA power, as exemplified above. This dynamical sharing of HSDPA power amongst cells sharing a power amplifier should be performed such that the HSDPA performance is improved.